1. Field of the Invention
The present invention relates to a rear wheel suspension device of a motorcycle in which a rear end portion of an upper arm member, which has a front end portion thereof pivotally supported on a vehicle body frame and extends rearwardly, is rotatably joined to an upper portion of a knuckle member, which pivotally supports a rear wheel. A rear end portion of a lower arm member, which has a front end portion thereof pivotally supported on the vehicle body frame and extends rearwardly, below the upper arm member is rotatably joined to a lower portion of the knuckle member.
2. Background of the Invention
Such a rear wheel suspension device has been known in JP-B-7-98507, for example. However, in the rear wheel suspension device disclosed in the above-mentioned JP-B-7-98507, one end of a rear cushion unit is mounted on a vehicle body frame, another end of the rear cushion unit is mounted on either one of an upper arm member and a lower arm member. Therefore, it is necessary to ensure a large rigidity of a joining portion of one end of the rear cushion unit to the vehicle body frame. In addition, in order to obtain a progressive cushion property, it is necessary to additionally provide the combination of a plurality of link members.